Glucosamine is a well-known amino monosaccharide found in chitin, glyco-proteins and glycosaminoglycans. Glucosamine is widely used for the treatment of rheumatic fever, arthritic and arthosic complaints, in the acute as well as chronic forms, as well as in the treatment of pathological conditions originating from metabolic disorders of the osteo-articular tissue. Although products in the marketplace are labeled as, or referred to as, “glucosamine”, they are misnomers since such products consist of glucosamine hydrochloride or as unreacted mixtures of glucosamine hydrochloride and a salt such as potassium or sodium sulfate.
Free glucosamine base may be prepared by the method recited in Chem. Ber., volume 75, page 1274. Such method involves the treatment of glucosamine hydrochloride with an ethanolic solution of a tertiary base such as triethylamine. Triethylamine hydrochloride is filtered off and the free glucosamine is then recovered from the reaction mixture. However, triethylamine is a toxic material even in small quantities and the yield of the free glucosamine base is quite low. Moreover, the free glucosamine base still contains residual chloride. Glucosamine hydrochloride may also be prepared by the method disclosed in U.S. Patent; the process involves the grinding of chitin to a very fine size, followed by digestion with concentrated hydrochloric acid. The crude glucosamine hydrochloride is then decolorized with activated charcoal and assayed by pH titration with a base.
N-acetylglucosamine may also be prepared by microbial fermentation. For example, see U.S. Pat. Nos. 5,998,173 and 6,693,188 as well as U.S. Published Patent Application Publication Nos. 2004/0091976 A1, 2004/0077055 A1 and 2003/0148998 A1. However, the microbial fermentation methods disclosed in the foregoing patents and published patent applications are complex, time-consuming and expensive to conduct. Furthermore, the microbial fermentation methods result in the production of various types of complex mixtures, requiring separation of the n-acetylglucosamine from the mixtures and purification of the separated n-acetylglucosamine.